Zirconium alloy



United dtates Patent ZIRCONIUM ALLOY Harley A. Wilhelm and David Peterson, Ames, Iowa, and Ralph F. Russi, Jr., Livermore, Calif., assignors to the United States of America as represented by the United States Atomic Energy Commission No Drawing. Application December 9, 1952 Serial No. 325,018

2 Claims. (Cl. 75-177) This invention deals with a zirconium alloy, and in particular with a binary zirconium-antimony alloy.

It is an object of this invention to provide a zirconium material which has a high corrosion resistance.

It is another object of this invention to provide a zirconium material of great hardness.

It is finally also an object of this invention to provide a zirconium material which has a 10W neutron-capture cross section.

These objects are accomplished by incorporating a small amount, preferably from 0.07 to 1.6% by weight, of antimony into zirconium; a quantity of from 0.1 to 0.5% gives the best results. The range of the antimony content is critical, since lesser as well as greater quantities yield alloys of a considerably reduced corrosion resistance.

The zirconium-antimony alloys cannot be prepared by simply melting the components,-as is cutomarily done in preparing alloys, because the boiling point of antimony is lower than the melting point of zirconium. A diffusion method has been developed, however, for the preparation of the zirconium-antimony alloys which has given satisfactory results. Crystal bar zirconium and powdered antimony, the latter in an excessive quanity with regard to the desired content, were heated for this purpose in a stainless steel bomb which was placed in a muflle furnace, and the metal mixture was heated therein for approximately 15 hours at about 825 C. The furnace was then cooled slowly. -A zirconium-antimony alloy, which showed great stability at elevated temperature, was formed. The content of the bomb was then melted in order to remove by distillation any antimony which had not been bonded to the zirconium.

By this difiusion method a master alloy was prepared which had a content of about 23% by weight of antimony. Various corrosion-resistant alloys having lower antimony content within the above-stated range were then made, from this master alloy by quasi diluting the latter with a corresponding amount of zirconium; this was done in melted condition in a graphite crucible. After this second alloying step the graphite crucible in most instances was found to adhere firmly to the alloy and it then had to be chipped off the alloy and the remainder to be removed with a wire brush. The metal piece was then bisected with a carborundurn wheel and the cross section was examined for homogeneity. If the alloy was found not to be homogeneous, it was remelted.

While the method just described proved to be the preferred method, other processes known to those skilled in the art may, of course, also be used. The alloys obtained may still be treated furthermore by annealing 5 at temperatures around 900 C. or higher, followed by slow cooling or quenching.

in order to test the corrosion resistance of the final zirconium-antimony alloys, samples thereof were polished and placed in a stainless steel bomb which was filled to one-third with distilled water. The bombs were closed and the samples were heated in the water to a temperature of 315 C. for various periods of time. In the following table the results of a number of these corrosion tests are compiled which were carried out with zirconium alloys of various antimony contents.

Weight increase of sample in mgJcmfil month after exposure to steam at 315 Sb content, percent by O. for-- weight 133-13 150-155 342493 400-450 hrs. hrs. hrs. hrs.

1 Some of oxide formed probably started to fall off.

It is obvious from this table that the antimony content of from 0.07 to 1.6% is actually critical, since the alloys having a lower or higher antimony content showed a considerably higher corrosion.

These alloys also had a great hardness which ranged from 55 to 65 Rockwell A scale, the higher hardness values within this range being obtained with alloys quenched from temperatures above 950 up to 1180 C.

The alloys of this invention have found use as construction material, and in particular as material for building equipment in the chemical industry on account of their high corrosion resistance. The alloys are also suitable for use in neutronic reactors, this on account of their low neutron-capture cross section.

It will be understood that this invention is not to be limited to the details given herein but that it may be modified within the scope of the appended claims.

What is claimed is:

1. As a new composition of matter, a binary zirconiumantimony alloy containing from 0.07% to 1.6% by weight of antimony.

2. The composition of matter of claim 1 wherein the antimony content ranges from 0.1 to 0.5%.

References Cited in the file of this patent UNITED STATES PATENTS 

1. AS A NEW COMPOSITION OF MATTER, A BINARY ZIRCONIUMANTIMORY ALLOY CONTAINING FROM 0.07% TP 1.6% BY WEIGHT OF ANTIMORY. 